Soil tester

ABSTRACT

Two cylinders telescopingly receive a third between them, one of the two is on a quadripod mount. Handles pull said two cylinders together and put air pressure on a soil engaging instrument. The greater the downward pull on the handles, the greater the air pressure and the greater the torque, through a helical cam, on the instrument. The top cylinder carries a recorder which marks a strip chart on a drum with the soil shear strength (torque) as a function of the vertical load (air pressure) on the instrument. The chart is carried on supply and take-up spools mounted on the underside of the recorder drum, slotted to permit chart movement.

United States Patent [191 Hawes SOIL TESTER [76] Inventor: Edward M. Hawes, 32418 Birkshire,

St. Clair Shores, Mich. 48082 [22] Filed: Sept. 6, 1972 [21] Appl. No.: 286,640

[52] US. Cl. 73/84, 73/88 E [51] Int. Cl. G01n 3/24 [58] Field of Search 73/88 E, 84, 101, 90, 99, 73/93 [56] References Cited UNITED STATES PATENTS 3,l 16,633 l/l964 Cohron 73/101 3,465,576 9/1969 Spanski 73/84 3,552,194 l/l97l Hawes 73/84 [451 Mar. 19, 1974 lri'mdry ExaminerCharles A. Ru ehl Ariana, Agent", 0rFirmEdward J. Kelly; Herbert Ber]; John F. Schmidt 57 ABSTRACT Two cylinders telescopingly receive a third between them, one of the two is on a quadripod mount. Handles pull said two cylinders together and put air pressure on a soil engaging instrument. The greater the downward pull on the handles, the greater the air pressure and the greater the torque, through a helical cam, on the instrument. The top cylinder carries a recorder which marks a strip chart on a drum with the soil shear strength (torque) as a function of the vertical load (air pressure) on the instrument. The chart is carried on supply and take-up spools mounted on the underside of the recorder drum, slotted to permit chart movement.

32 Claims, 15 Drawing Figures PATENTED MAR 19 I974 sum 02 or 11' PAIENTEDHAR 1 9 1914 3Q797l301 saw I 05 or 11 PATENTED MR 1 9 I974 sum 070F11 alv'evlam PATENTED MAR 1 9 I974 sum '08UF11 Pmlzmenm 1 9 1914 I 3.797 sum '09 HF 11 13m son. TESTER The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to means for measuring soil characteristics, especially to means to determine the shear strength of soils as a function of the load imposed on the soil. Soil characteristics are of interest to architects, highway engineers, builders of dams and levees, transportation engineers, rivers and harbors scientists, argicultural engineers, aerospace engineers, earth movers, and military personnel both tactical and strategic. Structural industries concerned with ground-contact equipment become increasingly dependent on statistics of soil characteristics for their equipment designs, and especially since static and dynamic structures tend to get heavier and taller, and since the most desirable soil areas tend to be occupied first, leaving more marginal soils as the only ones left to work on and with. Moreover, the rapidly increasing demand for greater mobility of a highly industrialized and densely populated society makes soil mechanics an important science and increases the need for reliable information regarding the characteristics and suitability of the varying types of terrain encountered.

2. The Prior Art The closest prior art known to the applicant is his own U.S. Pat. 3,552,194, issued Jan. 5, 1971, reissued July 17, 1973 as U.S. Pat. No. 27,696; U.S. Pat. No. 3,465,576 issued Sept. 9, 1969 to Paul I... Spanski; and U.S. Pat. No. 3,116,633 issued Jan. 7, 1964 to Gerald T. Cohron.

SUMMARY OF THE INVENTION A device to test and measure the shear strength of soil in situ comprises a basic support for the device, which basic support is itself mounted on-the soil being tested and measured. A soil engaging instrument is carried by the basic support, by means of a pressure fluid motor connected to exert downward pressure on the instrument. The instrument is rotated by a helicalcam and cam-follower mechanism actuated by down pressure on a pair of handles exerted through a resilient mechanism which varies the rotational effort directly as the operator presses down on the handles. A recording mechanism marks a chart to show soil shear strength (resistance to rotation of the soil engaging instrument) as a function of vertical load exerted on the instrument by the fluid motor.

The recording mechanism comprises a support, a cylindrical drum slotted throughout a substantial portion of its length and mounted on the support to oscillate about its cylindrical axis, a spring biasing the drum in one angular direction about its axis; a force to be recorded drives the drum in the opposite angular direction about its axis, a stylus carrier is mounted to move on a track parallel to the drum axis and holds a stylus in contact with the drum, a variable second force to be measured is connected to move the stylus carrier on its track, and means are provided to mount a strip chart and include a supply spool and a take-up spool in the drum, the chart passing from the supply spool through the slot, around the drum, and back through the slot onto the take-up spool.

THE DRAWINGS FIG. 1 is a front elevation view of a soil tester embodying the invention, with parts broken away and in section to show details.

FIGS. 2,3 and 4 are enlarged views in section of the structure shown in elevation in FIG. 1.

FIG. 5 is a top plan view of the recording device.

FIG. 6 is a view in section substantially on line 6 6 of FIG. 5.

FIG. 7 is a side elevation view of the recorder, being from the right side as seen in FIG. 5.

FIG. 8 is an enlarged elevation view from the plane of line 8 8 of FIG. 7.

FIG. 9 is a view in section substantially on line 9 9 of FIG. 1.

FIG. 10 is a sectional view similar to that of FIG. 3 but showing a portion of the helical camming mechanism and illustrating another embodiment of the camming mechanism.

FIGS. 11 and 12 are side and end elevation views respectively of a soil tester etc.

FIG. 13 is an enlarged view, in section, of the recording mechanism for the embodiment shown in FIGS. 11 and 12.

FIG. 14 is a graph showing a sample record of the type that can be produced by the recording device of this invention; and

FIG. 15 is a graph showing three sample records such as can be produced by my prior art soilv tester shown in U.S. Pat. No. 3,552,194.

DETAILED DESCRIPTION OF EMBODIMENT OF FIGS. l-9

As best seen in FIG. 1, a quadripod comprises a first means adapted to be supported by the soil being tested, and is made up of four telescoping legs 2, having upper ends hingedly secured at 4 to a mounting ring or collar 6, and lower ends fitted with suitable ground-engaging pads or feet 8. Each telescoping leg 2 is conveniently made up of an inner leg element 10 telescopingly engaging an outer leg element 12. Elements and 12 are held in a selected position by a pin 14 engaging suitable holes in the two leg elements.

A lower collar 16 is engaged by a hook 18 provided on each outer leg 12. Collars '6 and 16 are secured in any suitable manner to a cylinder 20 which has telescoping engagement with a second, smaller, cylinder 22. Cylinder 22 in turn telescopingly engages a third cylinder 24.

A collar 26 is secured to cylinder 24 and provides pivots for operator-operable levers. In the embodiment shown (FIG. 9), pivots 28 and 30 have threaded engagement with collar 26 at opposite ends of a diameter to provide pivot journals for levers 32 and 34 respectively, held in place by retainer screws 36. Preferably, the thickness (horizontal dimension in FIG. 9) of levers 32 and 34 is less than the axial length of the journals supporting the levers, in order that retainer screws 36 may be held tight without engaging the adjacent surfaces of the corresponding levers.

The lower ends of levers 32 and 34 pivotally engage the upper ends of links 38 and 40 respectively by means of pivot pins 42. The lower ends of links 38 and 40 engage the pivots 4 of two of the legs 2 of the quadripod.

A soil tester made according to this invention includes a soil-engaging instrument 44 carried at the lower end of a rod 46. Means to apply a downward load on instrument 44 are provided, and to that end an expansible chamber device includes a suitably packed piston 48 on the upper end of rod 46, and a cylinder 50 rotatably mounted in cylinder by means of combination radial and axial thrust, antifriction, bearings 52. Piston 48 and cylinder thus constitute a fluid pressure motor indicated as an assembly by 54.

Means for rotating instrument 44 are provided and include antifriction splines 56 which permit sliding of rod 46 relative to cylinder 50 but prevent relative rotation, whereby a torque applied to cylinder 50 drives rod 46 and instrument 44. If desired, the lower end ofcylinder 50 may be given additional radial support by an antifriction bearing 58.

At its upper end, cylinder 50 is secured to a flange 60 on a helical cam element 62 which is provided with a central bore 64 throughout its length. The external cylindrical surface is provided with a helical cam 66 which, in the embodiment shown, is two helical grooves formed in the surface. The cam follower of this cam mechanism comprises two rollers 68 riding in the grooves. Rollers 68 are rotatably mounted on cylinder 22 by means of pins 70. Cylinder 22 carries two other rollers 72 which ride in slots 74 in cylinder 20. As here shown, cylinder 22 carries rollers 72 by means of pins 76. A bushing 78 on the lower end of cylinder 22 coopcrates with another bushing 80 in the upper end of cylinder 20 to keep cylinders 20 and 22 in axial alignment.

Slots 74 in cylinder 20 are parallel to the cylinder axis and serve to hold cylinder 22 against the rotation which would occur in response to the torque on cylinder 22 imposed by rollers 68 riding in the grooves which form cam surfaces 66. Thus, rollers 72 riding in slots 74 provide the reaction force which compels cam element 62 to rotate, driving cylinder 50, rod 46, and instrument 44.

Bore 64 at its upper end is connected with a hose 82 which forms a bight 84 in the upper end of cylinder 22, passes through a slot 86, and connects with a pressure fitting 88 in cylinder 24. One end of a hose 90 is connected with fitting 88, and its other end is connected with a pressure regulator 92 having a gage 94 and an input T 96. A source of air under pressure is connected with T 96 by means of a hose 98, and an accumulator 100 is conventionally connected with regulator 92.

The pressure of the air delivered by regulator 92 to hose 90 is controlled by a suitable control valve, not shown, which is positioned by an actuator 102 carrying a cam follower 104. Follower 104 is conventionally biased into valve-closed position by a spring, not shown, and is moved against the bias of the spring by a cam 16 which is wedge-shaped and is grooved as at 108 to provide a track for cam folower 104.

Pressure regulator 92 may conveniently be mounted on a bracket or plate 110 which is held in place on cylinder 20 by a set screw 112. Plate 110 is provided with an aperture 114 to receive wedge-shaped cam 106. Aperture 114 is big enough in the plane of FIG. 3 to enable the desired actuation of cam follower 104.

Cam 106 is secured (FIG. 4) at its upper end to a boss 116 on cylinder 24 by means of a mounting tab 118 pivotally secured at 120 to cam 106 and a mounting screw 122 passing freely through tab 118 and having threaded engagement with boss 116. Jam nuts 124 hold screw 122 in a selected position and another jam nut 126 holds screw 122 against turning in boss 116. Collar 26 is preferably cut away at 128 to avoid interference with cam 106.

As noted above, cylinders 22 and 24 have a telescoping engagement, and bushings 130 and 132 maintain axial alignment of the cylinders during telescoping movement. The cylinders are held against relative angular movement by a pin and slot arrangement, here shown as pins 134 and 136 in the upper end of cylinder 22 engaging slots 138 and 140 in cylinder 24. A spring 142 is seated between a cap 144 on the upper end of cylinder 24 and a combination spring guide and seat which bears against the top of cylinder 22. More specifically, the combination guide and seat is mushroomshaped to provide the lower seat 146 secured to an elongated guide or stem 148 which engages an apertured boss 150 in cap 144. A projection 152 on the combination guide and seat engages an opening 154 in the top of cylinder 22.

' Reference will now be made to FIGS. 48 inclusive for a detailed description of the recording mechanism disclosed and claimed.

A bracket is apertured as at 162 to receive cylinder 24 to be supported thereby, being secured in any suitable conventional manner. Bracket 160, in turn, serves as a base or support for a drum 164 which is slotted throughout a major portion of its axial length as shown at 166.

The recording mechanism here disclosed and claimed produces a written or permanent record, conventionally referred to as a chart and usually made of paper. The chart is mounted on the drum in a manner to be described and is moved by the drum. To accomplish the desired movement, means are provided to rotate the drum about its cylindrical axis 168, including a pin secured in bracket 160, as for example by an interference fit. Pin 170 is provided with a suitably secured collar 172 which is disposed adjacent to the upper surface of bracket 160. The upper end of pin 170 is preferably square as shown at 174; see especially FIG. 5, wherein the cover of the recording mechanism is broken away to show the shape of pin end 174 in a top plan view.

Drum 164 is provided with a base 176, to which it is secured as by screws, one of which is shown at 178. Base 176 is centrally apertured to receive a flanged bearing bushing 180, of which flange 182 engages the lower face of base 176. A hub 184 is secured to the upper face of base 176 and surrounds bushing 180. A helical spring 186 is disposed in tension between hub 184 and a plate 188, being secured at its ends to hub 184 and plate 188 in any suitable manner. Plate 188 is provided centrally with a square opening to receive square end 174. A collar 190 is'secured to pin 170 below square end 174 by a set screw 192.

The external cylindrical surface of base 176 is grooved as shown at 194 to receive a cord 196 wrapped around the base and dead-ended at a suitable location on the periphery. By suitable is meant enough to enable rotation of drum 164 between stops 198 and 200. Stop 198 is here shown as secured to the underside of base 176, and stop 200 to the upper surface of bracket 160. As seen in FIG. 6, stop 200 is in front of stop 198, and the two stops touch; in FIG. 5, wherein the stops are shown as hidden by other structure, it can be seen that releasing cord 196 will rotate drum 164 clockwise, at which time stop 198 will move away from stop 200, and is in fact able to move through an arc approaching 360 until the stops again make contact, but at a virtually diametrically opposite point from the point of contact shown in FIG. 5.

Cord 196 wraps around drum 196 counterclockwise from its dead-end point such as point 202 in groove 194 and leaves the groove tangentially at or close to the same point 202. Then cord I96 wraps around a pulley 204 which is mounted to rotate about an axis perpendicular to bracket 160 so that cord 196 approaches and leaves pulley 204 in a plane parallel to bracket 160.

From pulley 204, cord 196 wraps around a pulley 206 which rotates about an axis parallel to the surface of bracket 160 and parallel to the aforesaid plane of approach and departure of the cord with respect to pulley 204. Cord 196 leaves pulley 206 in the downward direction as seen in FIG. 6, passes through an opening in collar 26, and is secured to cylinder at 208 as can be seen in FIG. 3.

Track-providing means 210, comprising an elongated element having grooves in opposed edges, can best be seen in FIGS. 5 and 7, secured to bracket 160 by screws 212. More specifically, an element 214 has opposed edges 216 in which are formed grooves 218, giving element 214 an H shape as seen in top plan (FIG. 5). The upper end of element 214 is slotted as at 220 to receive a pulley 222 rotatably mounted in slot 220.

A cluster of two pulleys 224 and 226 is mounted below bracket 160 by means ofa spring motor housing 228, on a shaft 230 having an axis of rotation 232. Pu]- ley 224 is coplanar with pulley 222, and pulley 226 rotates in a plane parallel to the plane of rotation of pulleys 222 and 224. Pulleys 224 and 226 are joined together and are secured to shaft 230, which is slotted to receive one end 234 of a spring 236, of which its remaining end 238 is secured to the underside of bracket 160. Still another pulley 240, coplanar with pulley 226, is mounted beneath bracket 160 and aligned with a slot 242 in the bracket.

A cord 244 is dead-ended on pin 136 (FIG. 4) by a screw 246, passes around pulley 240 after passing through slot 242, and then wraps around pulley 226 several times and is eventually dead-ended on pulley 226.

Still another cord 248 is dead-ended on and wraps around pulley 224, extends upward and passes over pulley 222, extends downward to and is dead-ended on a stylus carrier 250.

Stylus carrier 250 is adapted to move vertically on track-providing means 210, and to that end rotatably carries rollers 252 which run in grooves 218 in trackproviding means 210. Carrier 250 mounts a stylus 254 by means of a reservoir 256 pivotally supported on a C-shaped frame 258 which forms a part of the carrier. A spring 260 is secured to frame 258 and contacts stylus 254 to bias the stylus against the surface of drum 164, and thus into inking contact with a chart 262 wrapped around the drum.

FIG. 4 shows the recording means with a chart 262 in place wrapped around drum 164. In order to provide a better view of the structure, the chart is omitted from FIGS. 5-7.

As indicated above, drum 164 is slotted at 166 so that chart 262 may take the form of a continuous strip, fed from a supply spool inside the drum, out to the drum surface through slot 166, around the surface back to the slot, through the slot, and onto a take-up' spool inside the drum.

Slot 166 is open at the upper end of drum 164, and this construction gives the drum resilience in the radial direction, especially at its upper end. The opening at the upper end of drum 164 is adapted to be closed by a cover 264 having a stepped periphery to provide two substantially cylindrical surfaces 266 and 268. As is best seen in FIG. 6, surface 266 coincides with the external surface of drum 164, and cover surface 268 coincides with the internal surface 270 of drum 164. The dimensions of drum 164 and cover 264 are such that the resilience given to drum 164 by slot 166 permits cover 264 to engage the drum in a sliding fit, providing enough friction between surface 268 on cover 264 and surface 270 of drum 164 to prevent accidental displacement of cover 264. When a strip chart is in place around the outside of drum 164, the aforesaid sliding fit is aided by the frictional engagement of the drum by the chart.

As is best seen in FIG. 6, cover 264 is provided with two openings 272 and 274 to receive the upper ends of spools 276 and 278 respectively. The portions of spools 276 and 278 which extend above cover 264 are preferably of a smaller diameter to engage suitable bores in knobs 280 and 282, the knobs being here shown as held in place by set screws.

Collars 284 and 286 are secured to spools 276 and 278 respectively, and are spaced from the inner surface 283 to permit the use of friction washers 290 between collars 284, 286 and surface 288. Washers 290 are of a material such as cork, rubber, or the like, to aid in keeping spools 276 and 278 in a given position.

The space between collars 284, 286 and surface 288 is adjustable to some extent by the fact that knobs 280 and 282 can be adjusted longitudinally on the upper ends of their spools to compensate for wear of the friction washers 290. After the washers are worn so as to offer no useful resistance to slip of the spools relative to cover 264 when the space the washers occupy is a minimum, then the worn washer or washers should be replaced.

At their lower ends, spools 276 and 278 are provided with other collars 292 and 294, respectively. Lowerend collars 292 and 264 hold the strip chart off the base 176 and help to maintain alignment of the chart with slot 166. Spools 276 and 278 are slotted as at 296 and 298 respectively to receive the free ends of the strip chart for more secure winding onto the spools.

THE EMBODIMENT OF FIG. 10

The embodiment described above shows, in FIG. 3, rollers 72 to restrain cylinder 22 against rotation, and separately mounted rollers 68 engaging the helical grooves in helical cam element 62. FIG. 10 shows another embodiment in which rollers 72, which keep cylinder 22 from rotating, are coaxial with rollers 68' which engage the grooves in helical cam element 62'. This allows mounting both sets of rollers 68 and 72 in threaded bushings 300 engaging suitably threaded holes in guide bushings 78. The construction of the FIG. 10 embodiment is otherwise assumed to be the same as that of FIGS. 1-9.

THE EMBODIMENT OF FIGS 11-13 The invention disclosed above is illustrated in two configurations (FIGS. 1-10) that are adapted to test soil characteristics at or very close to the surface. FIGS. 11-13 disclose an embodiment of the invention that can be used to test soil characteristics at the bottom of a prepared (usually drilled) hole. In preparing supports for bridges, skyscrapers, and the like, it is often important to know the characteristics of the soil at different depths.

The embodiment shown in FIGS. Ill-13 uses equipment that is moved into position after the hole has been drilled by means of conventional equipment. Thus, FIGS. 11 and 12' show a portion of a mobile rig 310 having wheels two of which are shown at 312. An A- frame 314 is here shown mounted at each side of the frame 316. A rear cross member 318 of frame 316 is slotted at 320 to receive a conventional adjustable block 322. The two A-frames 314 support an upper cross member 324 parallel to cross member 318.

Member 324 is also slotted, as shown at 326, to receive a mounting block 328. It is contemplated that blocks 322 and 328 will be identical and therefore interchangeable. They are held in place by bolts 330, which engage conventional nuts held in the T-shaped slots 320 and 326. Such devices are old in the art and need not be detailed here.

Each of blocks 322, 328 is provided with a boss 332 permanently secured to the block as by welding. Each boss is bored to provide a socket to receive a shaft 334 in telescoping relation, and a set-screw 336 is provided to hold the shaft in any desired position in its socket.

A clamp 338 is pivotally secured to shaft 334 by a pin 340 and is provided with a threaded tightening means 342. Each clamp surrounds and is engageable with the cylinder 344 of a soil testing device embodying this invention in another form. Cylinder 344 telescopically receives a two-part shaft having an upper portion 346 which telescopes but does not rotate with respect to cylinder 344, and a lower portion 348 (a rod) which telescopes and is rotatable with respect to cylinder 344. The upper and lower portions 346 and 348 respectively are connected inside cylinder 344 by any suitable thrust and radial bearing mechanism, as shown for example in my above-identified prior art U.S. Pat. No. 3,552,194 wherein non-rotatable shaft 120 is connected with tubular portion 114 by means of structure including thrust bearing 122 and radial bearing 118, as seen in FIG. 1 of the patent and as described in the printed text, column 3, lines -14 of the original pa- I tent.

Means are provided to reciprocate telescopically the two-part shaft 346, 348 relative to cylinder 344. As shown, expansible chamber means are connected for that purpose, comprising fluid pressure motors 350 and upper and lower reaction members 352 and 354 respectively. More specifically, motors 350, in a preferred embodiment, may be hydraulic rams of which piston rods 356 are pivotally connected by means of pins 358 at their upper ends with reaction member 352, and cylinders 360 are pivotally connected by means of pins 362 with reaction member 354. Reaction members 352 and 354, in turn, are secured to upper portion 346 of the two-part shaft, and cylinder 344, respectively, in any suitable conventional manner.

Cylinders 360 are provided with connections 364 and 366 to receive and discharge operating fluid if doubleacting rams 350 are desired. Because the weight of the equipment connected with lower portion 348 of the two-part shaft will usually suffice to pull upper portion 346 down relative-to cylinder 344, rams 350 may if desired be single-acting, in which case only the fluid connections 364 will be required to enable lifting of the two-part shaft and its connected equipment, relative to cylinder 344. With single-acting rams, fluid would be admitted via connections 364 to lift the two-part shaft 346, 348 and the connected equipment; to lower the assembly, the operator would bleed fluid from cylinders 360 by means of suitable conventional valves.

As indicated above, upper and lower portions 346 and 348 of the two-part shaft are relatively rotatable. The downward motion of the two-part shaft relative to cylinder 344 is used to effect rotation of upper portion 346 relative to lower portion 348. Close to the lower end of cylinder 344, a collar 368 is affixed. Lower portion 348 of the two-part shaft is provided with a helical cam 370 having, as here shown, two helical grooves. Two cam followers in the form of rollers are held by collar 368 in engagement with the two helical grooves. In this respect, the helical cam and the two rollers which serve as cam followers are substantially the same as shown in the FIG. 3 illustration of the FIG. 1-9 embodiment, and as shown in FIG. 2 of my earlier U.S. Pat. No. 3,552,194.

This FIG. 11-13 embodiment of this invention adds an improvement over the invention disclosed and claimed in my aforesaid patent, wherein a clutch is described in column 2, lines 35-59. That clutch is eliminated in this FIG. 11-13 embodiment by the expedient of mounting the roller cam followers on shafts 372 which have threaded engagement with the collar 368. Consequently, the roller shafts may be turned so as to disengage the rollers from the helical grooves in case the soil tester is to be used to test load bearing strength only. To facilitate turning of the roller shafts, the outer ends of the roller shafts may be slotted as shown at 374 (FIG. 11) to receive an appropriately shaped tool.

The lower portion 348 of the two-part shaft carries a soil engaging instrument 44 which is identical to the instrument 44 in FIGS. 1 and 2 and described above. Because this FIGS. 11-13 embodiment is designed primarily to test soil at the bottom of a drilled hole into which a casing 376 has been driven, it will of course be understood that there may be a substantial distance between the lower end of helical cam 370 and instrument 44. Instrument 44 will be lowered by means of standard lengths of rod being added as the assembly is lowered. Such expedients are very old in the art of well drilling and need not be detailed here.

Because the instrument 44 and the below-described recording mechanism immediately above it are more delicate and more easily damaged than lengths of pipe or rod would be, a collar 378 is preferably secured to the lower shaft 348 as close as practicable to the recording mechanism. Collar 378 may be simply a steel torus held in place by a set screw, and in most cases that will suffice. If desired, collar 378 may be an antifriction bearing of suitable design. Also, it may be desirable in some cases to provide additional collars 380 spaced along the pipe, or possibly only one near the top of the casing,376 as shown in FIGS. 11 and 12.

The recording mechanism referred to above will now be described, with special attention to FIG. 13 where the mechanism is shown in detail. At its extreme lower end, rod (lower portion of the two-part shaft) 348 is centrally bored as at 382. The bored rod is slotted at opposite ends of a diameter as shown at 384. The slots terminate at their upper ends at 386 and at their lower ends at 388. A shaft 390 is reciprocable in bore 382 by means of bushings 392 and is held against rotation relative to rod 348 by rollers 394 riding in slots 384 and rotatably mounted on shafts 395 about an axis coincident with a diameter of shaft 390.

Thus rod 348 and shaft 390 constitute a pair of torque-transmitting elements rotatable in unison about a common axis and movable along their common axis relative to each other, with spring 398 connecting the pair for resiliently opposing said relative movement.

A flange 396 on rod 348 provides one seat for a helical spring 398, the other seat being a flange 400 at the lower end of shaft 390. Integral with the underside of flange 400 is a cylinder 402 having a central bore 404. An instrument shaft 406 is rotatable in bore 404 by means of bearing bushings 408 and 410. A thrust bearing 412 in the upper end of bore 404 engages the lower face of flange 400 and the upper end of shaft 406. Shaft 406 carries soil-engaging instrument 44 at its lower end. Spaced from instrument 44, a disc 414 is secured to shaft 406, as by a weldment 416. A collar 418 is also secured to shaft 406, as for example by a weldment.

Near the lower end of cylinder 402, a flange 420 is provided integral with cylinder 402. A helical spring 422 is seated between disc 414 and flange 420 and is secured at one end to collar 418 and at its other end to flange 420 so as to be able to transmit torque from cylinder 402 to shaft 406. A drum 424 is secured to disc 414 and extends upward therefrom to surround spring 422, cylinder 402, flange 400, and the lower end of spring 398.

Drum 424 is adapted to hold, on its external cylindrical surface, a removable chart such as graph paper or the like, shown at 426 in FIGS. 11 and 12. A scriber 428 is attached to flange 396 at 430 and is provided with an inwardly-directed point 432 in contact with the external surface of drum 424 or such chart as may be secured on the drum.

OPERATION EMBODIMENT OF FIGS. 1-9

To be sure that helical spring 186 is loaded throughout the operating stroke of drum 164, it is suggested that a preferred method of operation winds this spring through a distance greater than the arc through which drum 164 normally rotates. To provide further assurance that drum 164 rotates against spring tension throughout its operating arc, spring 186 is secured in such a way as to provide for a preload on the spring with cord 196 detached from its deadend 208. I

Thus, plate 188 is provided with a non-circular aperture to engage the non-circular end 174 of pin 170. In the drawings, drum 164 is shown in the position it occupies when the soil tester is ready to begin operating, but the operator has to put the drum into that position. The operator starts with the drum in a position not shown, namely with the drum turned clockwise so that, as seen in FIG. 5, stop 198 would be below stop 200, and as seen in FIG. 6, stop 198 would be in front of stop 200. Moreover, the stops should be in contact under the in fluence of spring 186.

If the operator finds play or space between stops 198 and 200 (with no tension in cord 196), he lifts plate 188 to disengage it from non-circular end 174 and turns the plate counterclockwise just enough to reengage the plate and the pin end. If the non-circular configuration is a square, the operator should try counterclockwise positions at intervals until he achieves an engagement such that spring 186 provides enough clockwise bias to drum 164 to keep stops 198 and 200 engaged, there being no tension at this time in cord 196.

Next, the operator pulls cord 196 down as seen in FIG. 3, rotating drum 164 counterclockwise as seen in FIG. 5 until stops 198 and 200 are again in contact in the position seen in FIG. 5, and fastens cord 196 to the dead-end 208 shown in FIG. 3. The tension in cord 196 should be rio more than required to contact stops 198 and 200, so that relative movement of cylinder 24 toward dead-end 208 immediately begins clockwise rotation of drum 164 under the influence of spring 186.

Attention is now directed to steps taken to put stylus carrier 250 into its starting position. Theoretically, spiral spring 236 should not be required to keep carrier 250 responsive to the tension in 'cord 244 because cord 244 is connected to lift carrier 250 against gravity. However, the gravity bias is usually small because the parts involved are small. Also, there is static friction in the means to mount the rotatable elements. These and other factors indicate the advisability of using some means such as spring 236 to oppose the pull on cord 244, even though it does not affect cord 248.

As in the case of drum operation described above, stylus carrier 250 is here shown in the position the elements have when the soil tester is ready to begin a test run, and of course the operator or somebody acting for him has to put the parts into the illustrated position.

The soil tester is preferably stored, overnight or longer, with cords 196 and 244 disconnected. In the case of cord 244, pulley cluster 226, 224, cord 248, and carrier 250, this means that carrier 250 will be as far down as it can go in FIGS. 1, 4, and 7, i. e., resting on the upper surface of bracket 160, under the influence of spiral spring 236 and gravity. As will be understood by those skilled in the art, the influence of spring 236 on carrier 250 at this stage is limited to a complete relaxation of tension in cord 248 because pulley 224 and cord 248 are incapable of transmitting a compressive force to carrier 250. Accordingly, the system does depend on gravity between carrier 250 and pulley 224.

The operator puts the parts into the position shown in FIG. 4 by reaving cords 244 and 248 as shown, and then by pulling on cord 244 enough to lift carrier 250 so that the carrier is free of bracket and so that stylus 254 is above the lower edge of chart 262, and secures cord 244 to cylinder 22 by means of dead-end 246. Spiral spring 236 is then under load and opposes further pull on cord 244.

Assuming that instrument 44 rests on a surface to be tested for its shear strength, the operator bears down on handles 32 and 34, in effect moving cylinder 24 down relative to cylinder 20. Such downward motion exerts a downward push on spring 142 (FIG. 4) and thus on cylinder 22. As is best seen in FIG. 3, cylinder 22 engages helical cam 66 by means of roller-cam'followers 68. Rotation of cylinder 22 is prevented by rollers 72 riding in slots 74, so that downward movement of cylinder 22 is resisted by whatever resistance to rotation (shear) is offered by the soil on which instrument 44 rests. If the soil shear strength is enough to prevent rotation of instrument 44 and helical cam 66, the downward push on cylinder 24 compresses spring 142 and thus increases the downward force on cylinder 22 and the torsional effort on cam 66 and instrument 44 until the effort-is great enough to overcome the resistance to shear of the soil.

As spring 142 compresses (FIG. 4), pin 136 moves upward relative to bracket 160, exerting a pull on cord 244 and lifting stylus carrier 250, so that the position of stylus 254 on chart 262 is a function of the shear strength of the soil being tested.

The resistance to shear of the soil is of course a function of the vertical load on instrument 44, which in turn is determined by the vertical component of the force exerted on the helical cams and normal thereto, and by the pressure in cylinder 54 acting on piston 48 (FIG. 3).

As cylinder 24 moves downward relative to cylinder 20, tapered cam 106 moves downward and cams the follower 104 (FIG. 3) leftward, opening valve 92 and admitting a greater pressure to cylinder 54, thus increasing the load on soil engaging instrument 44 and altering the resistance to shear of the soil.

As the stated relative movement between cylinders 24 and 20 occurs to shorten the distance between them, dead-end 208 at the upper end of cylinder 20 moves closer to bracket 160, and drum 164 rotates clockwise (FIG. 5) under the influence of helical spring 186 (FIG. 6), as cord 196 winds around drum 164 in groove 194. The further cam 106 moves downward as seen in FIGS. 3 and 4, the greater the opening of valve 92, the greater the arc through which drum 164 turns; because the resulting increase in pressure in cylinder 54 loads soil engaging instrument 44 more heavily, and the arc of rotation of drum 164 increases in proportion, it will be understood by those skilled in the art that the position of stylus 254 on chart 262 is a function of the vertical load on instrument 44.

FIG. 14 is a sample of the type of curve drawn by stylus 254 on chart 262, showing shear strength plotted against load. The vertical axis of the curve shows the load on instrument 44, and the horizontal axis is a measure of the shear strength of the soil, with the resulting curve providing information regarding soil shear strength at various loads.

FIG. 15 provides three samples of the type of information provided by my prior art soil tester disclosed and claimed in my U.S. Pat. No. 3,552,194. FIG. 15 is given here to show the differences between my present invention and the prior art. For a better understanding of soil testing in general and my prior art soil tester in particular, I incorporate by reference the doctoral thesis of Dr. Bong-sing Chang, titled A Method of Predicting the Soft Soil Performance of Off Road Vehicles," available from University Microfilms Library Services, P. O. Box 1346, Ann Arbor, Michigan, 48106, reference Dissertation Abstracts International for December, 1971, Volume 32, No. 6, page 3,3373.

In FIG. 15, the dash-dash line is the curve obtained by operating my prior art device so that the soilengaging instrument rotates while it is pushed into the ground. This curve shows the torque (right side vertical axis) needed to rotate the instrument at any given distance from the surface (called Sinkage) and shown by the horizontal axis. This curve is substantially a copy of a curve shown at FIG. 28 (b) of said dissertation.

The solid line on the FIG. 15 graph is the curve obtained by operating my prior art tester with no rotation of the soil-engaging instrument. This curve shows vertical load (left side vertical axis) at any given distance from the surface, called Sinkage and having values shown by the horizontal axis. This curve is substantially a copy of a curve shown at FIG. 28 (a) of said dissertation.

The dash-dot-dash line on the FIG. 15 graph is here presented to illustrate the difference between rotation and no rotation of the soil-engaging instrument. This curve also shows the vertical load necessary to penetrate the soil at a given depth from the surface, but with the soil-engaging instrument rotating. Thus, at x inches depth, it can readily be seen that the soil will support a much higher static load than one that contacts the soil with a shearing action. The dash-dotdash curve in FIG. 15 is not a reproduction of an actual test curve, but is a typical curve of the type discussed.

A key difference between my prior art tester and my present invention is that my prior art tester is intended to penetrate the soil (sinkage), whereas my present invention is primarily concerned with the measurement of soil shear strength without regard to penetration. For example, it may be desirable to measure the shear strength of a concrete road. It will be apparent that the soil tester here disclosed and claimed will effect substantially zero penetration, but also that it can very readily determine the shear strength of the road at various loads.

Reference was made above to the downward movement of handles 32 and 34 as being necessary to effect rotation of instrument 44 and that the force on cylinder 22 is increased by compression of spring 142 (due of course to spring 142 having a positive spring rate). It will also be recalled that diminution of the distance between cylinders 24 and 20 increases the vertical load on instrument 44, which has the effect of increasing the resistance to shear of the soil being tested. If it should turn out that spring 142 goes solid without achieving rotation of instrument 44, the operator will know that the initial pressure in cylinder 54 (with handles 32 and 34 fully raised) is too high and will take steps to reduce that initial pressure. In the usual situation, if the initial pressure in cylinder 54 is not too high, instrument 44 will turn with a minimum of force applied to handles 32 and 34. Furthermore, to minimize the chances of such an impasse, the lower end of cam 106 may be constructed to have zero taper for a short distance r, as shown, to enable increase in the force transmitted by spring 142 for such distance without increasing the pressure in cylinder 54.

OPERATION OF THE FIG. 10 EMBODIMENT The only significant difference in this embodiment is the use of structure that puts the rollers 68 and 72 on coincident axes instead of as shown in FIG. 3. Thus, rollers e and 72' are mounted and rotate on coincident axes.

OPERATION OF THE EMBODIMENT OF FIGS. 11-13 This embodiment of the invention fills a need that cannot readily be met with the structures shown in FIGS. l-lO. This FIGS. 11-13 embodiment can be used in places not accessible to the FIGS. l-l0 structures, such as a drilled hole; this embodiment does not require a source of compressed air to provide a vertical load; and this embodiment can be used as an attachment to the soil tester shown in my U.S. Pat. No. 3,552,194 supra.

Reference was made above to the two double-acting rams 350, which in the usual case would be hydraulic rams. My invention does not reside in the rams or any other part of the hydraulic system or in the system itself. Hydraulic systems are very highly developed, and it will be understood that a conventional system having a source of hydraulic fluid under pressure, a control valve, shut-off and isolation valves, hoses, tanks, one or more pressure regulating valves, etc will be connected in a conventional mannerand as required with rams 350.

It may be noted that rotation is imparted to the lower portion 348 of the two-part shaft by the helical cam and roller mechanism discussed above in much the same way as in my prior art patent, supra, and in much the same way as in the embodiments shown in FIGS. 1-10.

Referring to FIG. 13, those skilled in the art will observe that a vertical load is transmitted to soil-engaging instrument 44 through helical spring 398. The more spring 398 is compressed, the greater the load on element 44 and the lower the position of stylus point 432 on chart 426 (FIGS. 11 and 12), so that the position of point 432, in the vertical direction, is a function of the load on instrument (or element) 44.

Attention is now invited to the relationship between the force necessary to rotate instrument 44 and the vertical load on the instrument. If shaft 390 were lengthened and had instrument 44 fastened to its lower end, eliminating spring 422, and if spring 398 were also removed but with the retention of the slots 384 and rollers 394 to permitthe vertical movement of shaft 390 relative to shaft 348, then shaft 390 and instrument 44, having a finite weight, would apply a constant load on instrument 44 so long as rollers 394 had room to move upward in slots 384. The force required to turn instrument 44 would vary with the soil being tested, but would have no effect on the vertical load on instrument 44.

With the structure disclosed in FIGS. 11-13, rotation of instrument 44 lags behind the rotation of shaft 348, because of the shear strength of the soil engaged by instrument 44. The greater that shear strength, the greater the wind-up of spring 422 and the greater the compression of spring 398, with the result that the vertical load on instrument 44 is increased. Springs 398 and 422 and their connecting structure thus provide means to vary the vertical load on instrument 44 as a function of the force necessary to rotate instrument 44.

With lower portion 348 of the two-part shaft rotating and with no resistance to rotation applied to element 44, shafts 348 and 406 rotate together and there is no circumferential or angular movement of stylus 428 relative to drum 424 and chart 426. As soon as instrument 44 contacts a soil surface, there is resistance to rotation because of the soil shear strength, arid spring 422 yields angularly so that point 432 has angular movement on the chart that varies as the soil shear strength varies.

The composite of the relative vertical and angular movements of stylus point 432 on chart 426 produces a curve similar to that shown in FIG. 14, discussed above.

As pointed out above, this invention has for its primary purpose the measurement of soil shear strength. If an operator working with the FIGS. 1l13 embodiment should have occasion to test sinkage of a static load, he could be so by unscrewing the shafts 372,

FIGS. 11 and 12, to disengage the rollers (cam followers) from the helical cam 370.

I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

I claim:

1. A device to test the shear strength of soil in situ, comprising:

a. first means adapted to be supported by the soil being tested;

b. a soil-engaging instrument;

0. second means mounting said instrument on said first means and including i. third means to apply a downward load on said instrument, and I ii. fourth means for rotating said instrument;

d. operator-controlled means connected with the fourth means for applying such force as may be necessary to rotate the instrument;

e. means to measure said force to rotate; and

f. means to vary said load as a function of said force.

2. A device as in claim 1, wherein said third means includes a fluid pressure motor.

3. A device as in claim 2, wherein the fourth means includes a helically-wrapped cam element and a cam follower element in engagement therewith.

4. A device as in claim 3, wherein one of said elements is actuated by the operator-controlled means.

5. A device as in claim 4, wherein said mounting means includes a hollow member; said motor carried within and rotatable relative to said hollow member.

6. A test device as in claim 5, said motor comprising a cylinder and a piston; and means connecting the cylinder for rotation by the remaining one of said elements.

7. A device as in claim 2, wherein the operatorcontrolled means includes a connection with said first means, whereby at least a portion of the operatorcontrolled means is movable relative to said first means in the course of applying said instrument-rotating force.

8. A device asin claim 7, wherein the load-varying means includes a. a cam element;

b. a cam follower element;

0. a source of fluid under pressure;

d. a pressure regulator connected with said source and with said motor; and

e. means interconnecting the operator-controlled means, the cam and cam follower elements, and the regulator.

9. A device as in claim 8, wherein said second means includes first and second tubes having a telescoping relationship with each other and a third tube having a telescoping relationship with said second tube.

10. A device as in claim 1, wherein the fourth means includes a helically-wrapped cam element and a cam follower element in engagement therewith.

11. A device as in claim 10, wherein one of said elements is actuated by the operator-controlled means.

12. A device as in claim 11, wherein said mounting means includes a hollow member, and said load applying means includes an element carried within and rotatable relative to the hollow member.

' 13. A device as in claim 1, wherein said second means includes first and second tubes having a telescoping relationship with each other and a third tube having a telescoping relationship with said second tube.

14. A device as in claim 13, wherein said third means includes a fluid pressure motor.

15. A device as in claim 14, wherein said load varying means includes a cam element and a cam follower element in engagement with the cam element, one element mounted on the third tube and the other mounted on the first-mentioned tube whereby relative telescoping of the tubes imparts relative movement of said cam and cam follower elements.

16. A device as in claim 15, and a pressure fluid source and a pressure regulator connected to supply fluid under pressure to said motor, and means connecting said regulator for operation by said cam follower element.

17. A device as in claim 1, and means to record the required instrument-rotating force as a function of said downward load.

18. A device as in claim 17, wherein the recording means includes a chart having two axes, a stylus, means mounting the stylus for movement parallel to one of the two axes, and means to move the chart relative to the stylus in a direction parallel to the remaining one of the two axes.

19. A device as in claim 18, wherein the chart is mounted on a cylindrical drum, and wherein the chart moving means includes means to mount and rotate the drum about an axis of rotation.

20. A device as in claim 19, wherein the means to move the stylus and the means to rotate the drum comprise value indicators one of which is connected to indi cate and record the downward load on the soilengaging instrument and the other is connected to indicate and record said force to rotate the soil-engaging instrument.

21. A device as in claim 1, wherein the operatorcontrolled means comprises a fluid-pressure operated ram connected to raise and lower said third means.

22. A device as in claim 21, wherein said fourth means comprises two shafts relatively rotatable about a common axis and rotatable as a unit when said instrument encounters no resistance to rotation, and resilient means connecting the two shafts.

23. A device as in claim 22, wherein the force measuring means comprises a drum mounted on one of said two relatively rotatable shafts, and a stylus mounted on the other one of said two relatively rotatable shafts, the drum adapted to hold a sheet of recording material and the stylus adapted to contact said sheet.

24. A device as in claim 23, wherein the means to vary the load comprises a pair of torque-transmitting elements rotatable in unison about a common axis and movable along their common axis relative to each other, and a spring connecting the pair of torquetransmitting elements for resiliently opposing said relative movement along their common axis.

25. A device as in claim 24, wherein one of the two relatively rotatable shafts is also one of said pair of torque-transmitting elements. 7

26. A device as in claim 1, wherein said fourth means comprises two shafts relatively rotatable about a common axis and rotatable as a unit when said instrument encounters no resistance to rotation, and resilient means connecting the two shafts.

27. A device as in claim 26, wherein the force measuring means comprises a drum mounted on one of said two relatively rotatable shafts, and a stylus mounted on the other one of said two relatively rotatable shafts, the drum adapted to hold a sheet of recording material and the stylus adapted to contact said sheet.

28. A device as in claim 27, wherein the means to vary the load comprises a pair of torque-transmitting elements rotatable in unison about a common axis and movable along their common axis relative to each other, and a spring connecting the pair of torquetransmitting elements for resiliently opposing said relative movement along their common axis.

29. A device as in claim 28, wherein one of the two relatively rotatable shafts is also one of said pair of torque-transmitting elements.

30. A device as in claim 1, wherein the means to vary the load comprises a pair of torque-transmitting elements rotatable in unison about a common axis and movable along their common axis relative to each other, and a spring connecting the pair of torque- I d. a second shaft telescopingly engaging the firstnamed shaft;

e. a spring engaging both shafts for yieldingly transmitting axial thrust from the first shaft to the second shaft while permitting telescoping of the first and second shafts;

f. means for preventing relative angular movement of the first and second shafts during their relative axial telescoping movement;

g. a third shaft supported by the second shaft for rotation therewith about coincident axes;

means connecting the second and third shafts for transmitting axial thrust to the third shaft by the second shaft while preventing axial-movement of the second shaft relative to the first shaft;

i. spring means connecting the second and third shafts yieldingly to permit angular movement of the third shaft relative to the second shaft while the second shaft resiliently applies a torque to the third shaft; and

j. means connecting the first and third shafts to indicate said relative axial movement as a function of transmitted axial thrust and said relative angular movement as a function of transmited torque.

32. A device as in claim 31, wherein the indicating means connecting the first and third shafts comprises a drum mounted on and movable with one of said shafts; and a stylus mounted on and movable with the remaining one of said shafts. 

1. A device to test the shear strength of soil in situ, comprising: a. first means adapted to be supported by the soil being tested; b. a soil-engaging instrument; c. second means mounting said instrument on said first means and including i. third means to apply a downward load on said instrument, and ii. fourth means for rotating said instrument; d. operator-controlled means connected with the fourth means for applying such force as may be necessary to rotate the instrument; e. means to measure said force to rotate; and f. means to vary said load as a function of said force.
 2. A device as in claim 1, wherein said third means includes a fluid pressure motor.
 3. A device as in claim 2, wherein the fourth means includes a helically-wrapped cam element and a cam follower element in engagement therewith.
 4. A device as in claim 3, wherein one of said elements is actuated by the operator-controlled means.
 5. A device as in claim 4, wherein said mounting means includes a hollow member; said motor carried within and rotatable relative to said hollow member.
 6. A test device as in claim 5, said motor comprising a cylinder and a piston; and means connecting the cylinder for rotation by the remaining one of said elements.
 7. A device as in claim 2, wherein the operator-controlled means includes a connection with said first means, whereby at least a portion of the operator-controlled means is movable relative to said first means in the course of applying said instrument-rotating force.
 8. A device as in claim 7, wherein the load-varying means includes a. a cam element; b. a cam follower element; c. a source of fluid under pressure; d. a pressure regulator connected with said source and with said motor; and e. means interconnecting the operator-controlled means, the cam and cam follower elements, and the regulator.
 9. A device as in claim 8, wherein said second means includes first and second tubes having a telescoping relationship with each other and a third tube having a telescoping relationshiP with said second tube.
 10. A device as in claim 1, wherein the fourth means includes a helically-wrapped cam element and a cam follower element in engagement therewith.
 11. A device as in claim 10, wherein one of said elements is actuated by the operator-controlled means.
 12. A device as in claim 11, wherein said mounting means includes a hollow member, and said load applying means includes an element carried within and rotatable relative to the hollow member.
 13. A device as in claim 1, wherein said second means includes first and second tubes having a telescoping relationship with each other and a third tube having a telescoping relationship with said second tube.
 14. A device as in claim 13, wherein said third means includes a fluid pressure motor.
 15. A device as in claim 14, wherein said load varying means includes a cam element and a cam follower element in engagement with the cam element, one element mounted on the third tube and the other mounted on the first-mentioned tube whereby relative telescoping of the tubes imparts relative movement of said cam and cam follower elements.
 16. A device as in claim 15, and a pressure fluid source and a pressure regulator connected to supply fluid under pressure to said motor, and means connecting said regulator for operation by said cam follower element.
 17. A device as in claim 1, and means to record the required instrument-rotating force as a function of said downward load.
 18. A device as in claim 17, wherein the recording means includes a chart having two axes, a stylus, means mounting the stylus for movement parallel to one of the two axes, and means to move the chart relative to the stylus in a direction parallel to the remaining one of the two axes.
 19. A device as in claim 18, wherein the chart is mounted on a cylindrical drum, and wherein the chart moving means includes means to mount and rotate the drum about an axis of rotation.
 20. A device as in claim 19, wherein the means to move the stylus and the means to rotate the drum comprise value indicators one of which is connected to indicate and record the downward load on the soil-engaging instrument and the other is connected to indicate and record said force to rotate the soil-engaging instrument.
 21. A device as in claim 1, wherein the operator-controlled means comprises a fluid-pressure operated ram connected to raise and lower said third means.
 22. A device as in claim 21, wherein said fourth means comprises two shafts relatively rotatable about a common axis and rotatable as a unit when said instrument encounters no resistance to rotation, and resilient means connecting the two shafts.
 23. A device as in claim 22, wherein the force measuring means comprises a drum mounted on one of said two relatively rotatable shafts, and a stylus mounted on the other one of said two relatively rotatable shafts, the drum adapted to hold a sheet of recording material and the stylus adapted to contact said sheet.
 24. A device as in claim 23, wherein the means to vary the load comprises a pair of torque-transmitting elements rotatable in unison about a common axis and movable along their common axis relative to each other, and a spring connecting the pair of torque-transmitting elements for resiliently opposing said relative movement along their common axis.
 25. A device as in claim 24, wherein one of the two relatively rotatable shafts is also one of said pair of torque-transmitting elements.
 26. A device as in claim 1, wherein said fourth means comprises two shafts relatively rotatable about a common axis and rotatable as a unit when said instrument encounters no resistance to rotation, and resilient means connecting the two shafts.
 27. A device as in claim 26, wherein the force measuring means comprises a drum mounted on one of said two relatively rotatable shafts, and a stylus mounted on the other one of said two relatively rotatable shafts, the drum adapted to hold a sheet of recording material and the stylus adapted to contact said sheet.
 28. A device as in claim 27, wherein the means to vary the load comprises a pair of torque-transmitting elements rotatable in unison about a common axis and movable along their common axis relative to each other, and a spring connecting the pair of torque-transmitting elements for resiliently opposing said relative movement along their common axis.
 29. A device as in claim 28, wherein one of the two relatively rotatable shafts is also one of said pair of torque-transmitting elements.
 30. A device as in claim 1, wherein the means to vary the load comprises a pair of torque-transmitting elements rotatable in unison about a common axis and movable along their common axis relative to each other, and a spring connecting the pair of torque-transmitting elements for resiliently opposing said relative movement along their common axis.
 31. A soil testing device comprising: a. a platform; b. a shaft; c. means mounting the shaft on the platform and for simultaneously rotating the shaft and moving it along its axis of rotation; d. a second shaft telescopingly engaging the first-named shaft; e. a spring engaging both shafts for yieldingly transmitting axial thrust from the first shaft to the second shaft while permitting telescoping of the first and second shafts; f. means for preventing relative angular movement of the first and second shafts during their relative axial telescoping movement; g. a third shaft supported by the second shaft for rotation therewith about coincident axes; h. means connecting the second and third shafts for transmitting axial thrust to the third shaft by the second shaft while preventing axial movement of the second shaft relative to the first shaft; i. spring means connecting the second and third shafts yieldingly to permit angular movement of the third shaft relative to the second shaft while the second shaft resiliently applies a torque to the third shaft; and j. means connecting the first and third shafts to indicate said relative axial movement as a function of transmitted axial thrust and said relative angular movement as a function of transmited torque.
 32. A device as in claim 31, wherein the indicating means connecting the first and third shafts comprises a drum mounted on and movable with one of said shafts; and a stylus mounted on and movable with the remaining one of said shafts. 